Preparation of diglycerides



' ethers, etc.

Patented Sept. 26, 1950 PREPARATION OF DIGLYCERIDES Ernest B. Kester,Berkeley, -Calif., assignor to the United States of America asrepresented by the Secretary of Agriculture No Drawing.

Claims.

Application January 25, 1949, Serial No. 72,737

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G; 757) This application is made under the act of March 3, 1883, asamended by the act of April 30, 1928, and the invention hereindescribed, if patented in any country, may be manufactured and used byor for the Government of the United States of America for governmentalpurposes throughout the world without the payment to me of any royaltythereon.

This invention relates to diglycerides having the structural formulawhere R and R are the same or different aliphatic radicals containing atleast 7 carbon atoms, and has among its objects the preparation of theseesters in a substantially pure form by a simple and economical process.

Known methods for preparing compounds of the above type are notsatisfactory because they produce mixtures of mono, di, andtriglycerides, or, to obtain an individual compound itis necessary touse expensive reagents such as trityl One known method involves-heatinga triglyceride with glycerine and a catalyst such as sulphuric acid.This technique produces a mixture of mono, di, and triglycerides whichis exceedingly difficult to resolve. Further, if the acyl groups on thestarting material are different from one another (mono-lauryl, distearylglyceride, for example) then the product will contain a myriad ofcompounds differing in type of acyl radical, number of acyl radicals,position of acyl radicals, etc. Another known method involves reactingan alpha monoglyceride with a chloride of a fatty acid in the presenceof pyridine as a hydrochloric acid acceptor. This process is likewisenot clean-cut but produces a mixture of glycerides difiering as tonumber and position of the respective acyl radicals.

It has now been found that diglycerides of the aforesaid type can beprepared in a simple and expeditious manner by reacting a glycidyl esterof an aliphatic carboxylic acid with an aliphatic carboxylic acid. Thereaction which occurs can be represented by the following equation,wherein R and R have the significance above indicated:

0 O CHi-O- R O CHr-O-R H Elm-( R H-OH O H2-OO R s. t

(glycidyl ester) (acid) (formed diglyceride) One advantage of my processis that a single compound is produced. In every case the product is thealpha, gamma diglyceride desired. There is no need to carry outlaborious separations as with prior methods.

Another advantage of my process is that alpha, gamma diglycerides areproduced exclusively. When glycerol or a'monoglyceride is used as areactant such a limited result cannot be achieved but the product maycontain alpha, beta derivatives as well as alpha, gamma derivatives.

A further advantage of my process is its simplicity in that it is notnecessary to employ any catalysts. A mere heating of the reagents, ifdesired in the presence of a solvent, is all that is required. The fattyacid which is used as a reactant directly is low in price in comparisonto the acyl chlorides or trityl derivatives employed in previousmethods.

Another advantage of my process is that it is particularly adapted toproduce in one step a diglyceride in which the acyl radicals aredifferent. By choice of the proper fatty acid and the proper glycidylester, any desired alpha, gamma diglyceride can be synthesized.

A further advantage of my process lies in the fact that the reactantsneed not be anhydrous.

Contrary to most of the known syntheses, ordinary reagents may be usedin my process Without necessity for removal of the usual'traces of waterpresent in all commercial reagents.

The following examples illustrate the claimed process applied toparticular materials under particular conditions. It is to be understoodthat these examples are submitted only by way of illustration and notlimitation.

EXAMPLE I Preparation of glycer l alpha, gamma laurostear'ate 20.4 g.(0.08 mol) of glycidyl laurate and 11.4 g. (0.04 mol) of stearic acidwere mixed and heated for four hours at 128 to 130 C. At the end of thisperiod, it was determined by titration of an aliquot sample of thereaction product that all but 2.6% of the stearic acid had reacted.

The reaction product was dissolved in hot absolute alcohol and oncooling 5.1 grams (25.4% yield) of alpha-lauryl, amma stearyl ester ofglycerol was obtained by filtering out the formed crystals. The producthad a melting point of 62-64 C. and a saponification equivalent weightof 271.5 (calculated 270.35). By recrystallization of the mother liquor,additional amounts of the product could be obtained.

EXAIWPLE II Preparation of glycerol alpha, gamma erucostearate 85 g.(0.251 mol) of erucic acid and g.

3 (0.502 mol) of glycidylstearate were added to 1 liter of chlorobenzeneas the solvent contained in a 2-liter flask equipped with refluxcondenser.

The mixture was refluxed for 28 hours. end of this time, a titratedsampleshowed the reaction to be 99% complete.

The solvent was removed by about 20 mm. Hg pressure. The residue, 260g., was dissolved in 780 ml. of hot hexane and crystallized by coolingto 23-25 'C." The'product was washed with hexane and air-dried. A secondcrop was obtained by concentrating the mother liquor to half its volumeand cooling.

At the disuiiatid at 5 .gamma-stearyl glyceride, is particularly adaptedThe two crops were combined and'crystallized from hexane and then'ffromabsolute alcohol. The purified product, alpha erucyl, gamma stearylglyceride weighed 65 g. (40% yield) and had a melting point of 5657 C.Analysis; C, 76.1%; H, 12.1%; iodine Va1ue 36.2; saponificationequivalent weight, 3 11. (Theoretical: C, 76%; H, 11.73%;iodine value,37.3; saponification equivalent weight, 339.54)

, The process herein disclosed is simple in that it merely involvescontacting of the glycidyl ester and fatty acid-under the influence ofheat. In general, temperatures from about 50 C. to about 200 0,,preferably from about ;100 C. to about 200 C. are suitable. To promotecontact between the reactants it ispreferred to employ a solvent. Ingeneral inert, hydrophobic organic solvent can be :used such as benzene,chlorobenzenetoluene, Xylenes, aliphatic hydrocarbons such as hexane,octane or mixtures of hydrocarbons such as petroleum ether, gasoline,naphtha, benzine, etc. When using a solvent it is preferred to refluxthe reaction mixture to prevent loss of solvent. In such case thetemperature of reaction will-be approximately equal to the boiling pointof the solvent. In general the glycidylreactant and fatty acid may be employed in equimolecular proportions. However, it is preferred to employthe glycidyl reactant in excess. The reason for this is that thereby thereaction time is diminished and the excess glyc idyl reactant caneasilybe recovered from the reaction mixture by distillation under reducedpressure. 7 'Iheglycidyl reactant so recoveredcan beusedto preparefurther quantities of the diglyceride. I v V v I The novel process is ofwide versatility and can be used to prepare a wide variety of alpha,gamma dig1ycerides--byselection of the proper reactants. As the glycidolreactant one may use any glycidyl ester of .analiphatic carboxylic acidcontaining at least 8 carbon atoms. Suitable reactants are, for example,glycidyl caprylate, glycidyl pelargonate, glycidyl caprate, glycidylundecylate, glycidyl laurate, glycidyl tridecylate, glycidyl myristate,glycidyl pentadecylate, glycidyl palmitate, glycidyl margarate, glycidylstearate, glycidyl nonadecylate, glycidyl arachidate, glycidyl oleate,glycidyl elaidate, glycidyl rioinoleate, glycidyl palmitoleate, glycidylerucate, glycidyl brassidate, glycidyl linoleate, and so forth.

As the fatty acid reactant, one may use any aliphatic carboxylic acidcontaining at least 8 carbon atoms. Suitable acids are, for example,caprylic, pelargonic, capric, undecylic, lauric,

tridecylic, myristieppentadecylic, palmitic, stearic, margaric,nondecyliq arachidic, oleic, elaidic,

to be converted into a compound useful for emulsifying and dispersingpurposes. To this end the glyceride is converted into its aminoethylglycerophosphoric acid ester by the process as set forth in U. S.Patents 2,436,699 and 2,447,715 to W. G. Rose.

Having thus described the invention, what is claimed is:

1. A process comprising heating to a temperature from about 50 C. toabout 200 C. a reaction mixture of a glycidyl ester having the forwhereR and R, are aliphatic radicals containing at least 7 carbon atoms, toproduce a diglyceride having the formula 2. The process of claim 1wherein the reaction mixture contains an inert organic solvent and isrefluxed during the heating.

"3,. The process of claim 2 wherein an excess, ofthe glycidyl ester isused.

4; Av process comprising heating to a temperature from about 50 C. toabout 200 C. a reaction mixture of glycidyl stearate and erucic acid toproduce glycerol alpha, gamma erucostearate.

5; The process of claim 4 wherein the reaction mixture contains aninert, organic solvent,

an excess of glycidyl stearate is used, and the.

mixture is refluxed during heating.

ERNEST B. KESTIER.

REFERENCES CITED The following references are of record in the Daubertet al., Oil & Soap, Feb. 1944,1315. 42-46.

Orthner et a1. .S-ept. 27, 1938"

1. A PROCESS COMPRISING HEATING TO A TEMPERATURE FROM ABOUT 50*C. TO ABOUT 200*C. A REACTION MIXTURE OF A GLYCIDYL ESTER HAVING THE FORMULA 